Voltage transients at a voltage higher than the normal voltage and higher than the voltage that circuits can withstand without damage can occur on the power supply line of electronic circuits. This occurs, for example, in the automotive field. Electronic circuits, particularly half-bridge and bridge circuits, must be protected against these dangerous voltages.
FIG. 1 illustrates a bridge or half-bridge electronic circuit, designated by the reference numeral 100, connected to a power supply voltage source Vs. Rs designates the internal resistance of the power supply voltage source Vs, while Va designates the power supply terminal of the electronic circuit 100. The chart associated with FIG. 1 plots the power supply voltage Vs, including transients whose voltage is higher than the normal voltage. The method normally used to protect electronic circuits against high-voltage transients on the power supply line consists in adding an adapted transient suppression device.
FIG. 2 illustrates the prior art of adding a transient suppression device, designated by the reference numeral 200. The transient suppression circuit 200 is thus placed between the power supply terminal Va of the circuit and ground. The chart shows that when the voltage Va reaches the value Vm, a value that will not damage the electronic circuit 100, the transient suppression device 200 limits the voltage Va to the value Vm. The suppression device 200 must therefore be able to absorb the energy of the voltage transient and must therefore contain additional high-voltage power components which are bulky and expensive.